ABSTRACT Every year there are an estimated 7.9 million children born with a serious birth defect and 3.3 million of these are children under five years of age who die from factors related to their birth defect. Comprehensive, reliable data on birth defects are not available for most developing countries. In many resource-poor settings, the baseline prevalence of birth defects is not known and systematic monitoring for birth defects is difficult or non- existent. Antiretroviral treatment (ART) in pregnancy can maximally reduce the risk of vertical transmission of HIV, and therefore it is recommended that all pregnant women with HIV receive effective ART regimens to prevent the transmission of HIV to their infants. However, there have been concerns about the possibility of women on ART at conception or during the first trimester having an increased risk of delivering an infant with a birth defect. The goal of this proposal is to establish a birth defect hospital based surveillance program in Kampala, Uganda and to determine the prevalence of major external birth defects and association of maternal risk factors including antiretroviral therapy to these defects. Four hospitals in Kampala, Uganda will be included in the surveillance system with approximately 48,000 deliveries per year. Informative births (live and stillborn) regardless of gestational age that are born at the four hospitals will be included in the surveillance project for a duration of five years. Informative births are those in which the newborn is formed well enough to ascertain whether or not there is a birth defect. Each newborn will be examined as soon as possible after birth. Infant measurements (weight, head circumference and length) will be obtained and all newborns will be examined for major external birth defects by trained midwives. Newborns with major external birth defects will be photographed after obtaining consent and the photographs will be used to classify the diagnosis. As needed, the photos and verbatim descriptions will be sent to birth defect experts for confirmation of diagnoses and for coding of the birth defect using ICD-10 disease classification criteria. Demographic information, HIV status and obstetric information (parity status, previous live and still births, presence of physical defects of births of previous children) will be collected for all mothers. Every mother of an infant identified with a major external birth defect of interest will be asked to participate in a case-control study. Three controls will be selected for each case matched on hospital of delivery. After consenting, each mother will be asked to respond to questions regarding, types of medications taken during pregnancy including antiretroviral drugs and cotrimoxazole, medical history and more detailed demographic information. The surveillance program will provide crucial current data on the baseline prevalence of birth defects in Uganda while the case-control study will allow examination of the possible effects of antiretroviral treatment on infant outcomes while also screening for other common known causes of birth defects.